/*
 * libipq.c
 *
 * IPQ userspace library.
 *
 * Please note that this library is still developmental, and there may
 * be some API changes.
 *
 * Author: James Morris <jmorris@intercode.com.au>
 *
 * Copyright (c) 2000-2001 Netfilter Core Team
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>

#include "libipq.h"

/****************************************************************************
 *
 * Private interface
 *
 ****************************************************************************/

enum {
    IPQ_ERR_NONE = 0,
    IPQ_ERR_IMPL,
    IPQ_ERR_HANDLE,
    IPQ_ERR_SOCKET,
    IPQ_ERR_BIND,
    IPQ_ERR_BUFFER,
    IPQ_ERR_RECV,
    IPQ_ERR_NLEOF,
    IPQ_ERR_ADDRLEN,
    IPQ_ERR_STRUNC,
    IPQ_ERR_RTRUNC,
    IPQ_ERR_NLRECV,
    IPQ_ERR_SEND,
    IPQ_ERR_SUPP,
    IPQ_ERR_RECVBUF,
    IPQ_ERR_TIMEOUT
};
#define IPQ_MAXERR IPQ_ERR_TIMEOUT

struct ipq_errmap_t {
    int errcode;
    char *message;
} ipq_errmap[] = {
    {
    IPQ_ERR_NONE, "Unknown error"}
    , {
    IPQ_ERR_IMPL, "Implementation error"}
    , {
    IPQ_ERR_HANDLE, "Unable to create netlink handle"}
    , {
    IPQ_ERR_SOCKET, "Unable to create netlink socket"}
    , {
    IPQ_ERR_BIND, "Unable to bind netlink socket"}
    , {
    IPQ_ERR_BUFFER, "Unable to allocate buffer"}
    , {
    IPQ_ERR_RECV, "Failed to receive netlink message"}
    , {
    IPQ_ERR_NLEOF, "Received EOF on netlink socket"}
    , {
    IPQ_ERR_ADDRLEN, "Invalid peer address length"}
    , {
    IPQ_ERR_STRUNC, "Sent message truncated"}
    , {
    IPQ_ERR_RTRUNC, "Received message truncated"}
    , {
    IPQ_ERR_NLRECV, "Received error from netlink"}
    , {
    IPQ_ERR_SEND, "Failed to send netlink message"}
    , {
    IPQ_ERR_SUPP, "Operation not supported"}
    , {
    IPQ_ERR_RECVBUF, "Receive buffer size invalid"}
    , {
    IPQ_ERR_TIMEOUT, "Timeout"}
};

static int ipq_errno = IPQ_ERR_NONE;

static ssize_t ipq_netlink_sendto(const struct ipq_handle *h,
				  const void *msg, size_t len);

static ssize_t ipq_netlink_recvfrom(const struct ipq_handle *h,
				    unsigned char *buf, size_t len,
				    int timeout);

static ssize_t ipq_netlink_sendmsg(const struct ipq_handle *h,
				   const struct msghdr *msg,
				   unsigned int flags);

static char *ipq_strerror(int errcode);

static ssize_t
ipq_netlink_sendto(const struct ipq_handle *h, const void *msg, size_t len)
{
    int status = sendto(h->fd, msg, len, 0,
			(struct sockaddr *) &h->peer, sizeof(h->peer));
    if (status < 0)
	ipq_errno = IPQ_ERR_SEND;
    return status;
}

static ssize_t
ipq_netlink_sendmsg(const struct ipq_handle *h,
		    const struct msghdr *msg, unsigned int flags)
{
    int status = sendmsg(h->fd, msg, flags);
    if (status < 0)
	ipq_errno = IPQ_ERR_SEND;
    return status;
}

static ssize_t
ipq_netlink_recvfrom(const struct ipq_handle *h,
		     unsigned char *buf, size_t len, int timeout)
{
    int addrlen, status;
    struct nlmsghdr *nlh;

    if (len < sizeof(struct nlmsgerr)) {
	ipq_errno = IPQ_ERR_RECVBUF;
	return -1;
    }
    addrlen = sizeof(h->peer);

    if (timeout != 0) {
	int ret;
	struct timeval tv;
	fd_set read_fds;

	if (timeout < 0) {
	    /* non-block non-timeout */
	    tv.tv_sec = 0;
	    tv.tv_usec = 0;
	} else {
	    tv.tv_sec = timeout / 1000000;
	    tv.tv_usec = timeout % 1000000;
	}

	FD_ZERO(&read_fds);
	FD_SET(h->fd, &read_fds);
	ret = select(h->fd + 1, &read_fds, NULL, NULL, &tv);
	if (ret < 0) {
	    if (errno == EINTR) {
		return 0;
	    } else {
		ipq_errno = IPQ_ERR_RECV;
		return -1;
	    }
	}
	if (!FD_ISSET(h->fd, &read_fds)) {
	    ipq_errno = IPQ_ERR_TIMEOUT;
	    return 0;
	}
    }
    status = recvfrom(h->fd, buf, len, 0,
		      (struct sockaddr *) &h->peer, &addrlen);
    if (status < 0) {
	ipq_errno = IPQ_ERR_RECV;
	return status;
    }
    if (addrlen != sizeof(h->peer)) {
	ipq_errno = IPQ_ERR_RECV;
	return -1;
    }
    if (status == 0) {
	ipq_errno = IPQ_ERR_NLEOF;
	return -1;
    }
    nlh = (struct nlmsghdr *) buf;
    if (nlh->nlmsg_flags & MSG_TRUNC || nlh->nlmsg_len > status) {
	ipq_errno = IPQ_ERR_RTRUNC;
	return -1;
    }
    return status;
}

static char *ipq_strerror(int errcode)
{
    if (errcode < 0 || errcode > IPQ_MAXERR)
	errcode = IPQ_ERR_IMPL;
    return ipq_errmap[errcode].message;
}

/****************************************************************************
 *
 * Public interface
 *
 ****************************************************************************/

/*
 * Create and initialise an ipq handle.
 * FIXME: implement flags.
 */
struct ipq_handle *ipq_create_handle(u_int32_t flags)
{
    int status;
    struct ipq_handle *h;

    h = (struct ipq_handle *) malloc(sizeof(struct ipq_handle));
    if (h == NULL) {
	ipq_errno = IPQ_ERR_HANDLE;
	return NULL;
    }
    memset(h, 0, sizeof(struct ipq_handle));
    h->fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_FIREWALL);
    if (h->fd == -1) {
	ipq_errno = IPQ_ERR_SOCKET;
	close(h->fd);
	free(h);
	return NULL;
    }
    memset(&h->local, 0, sizeof(struct sockaddr_nl));
    h->local.nl_family = AF_NETLINK;
    h->local.nl_pid = getpid();
    h->local.nl_groups = 0;
    status = bind(h->fd, (struct sockaddr *) &h->local, sizeof(h->local));
    if (status == -1) {
	ipq_errno = IPQ_ERR_BIND;
	close(h->fd);
	free(h);
	return NULL;
    }
    memset(&h->peer, 0, sizeof(struct sockaddr_nl));
    h->peer.nl_family = AF_NETLINK;
    h->peer.nl_pid = 0;
    h->peer.nl_groups = 0;
    return h;
}

/*
 * No error condition is checked here at this stage, but it may happen
 * if/when reliable messaging is implemented.
 */
int ipq_destroy_handle(struct ipq_handle *h)
{
    if (h) {
	close(h->fd);
	free(h);
    }
    return 0;
}

int ipq_set_mode(const struct ipq_handle *h, u_int8_t mode, size_t range)
{
    struct {
	struct nlmsghdr nlh;
	ipq_peer_msg_t pm;
    } req;

    memset(&req, 0, sizeof(req));
    req.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(req));
    req.nlh.nlmsg_flags = NLM_F_REQUEST;
    req.nlh.nlmsg_type = IPQM_MODE;
    req.nlh.nlmsg_pid = h->local.nl_pid;
    req.pm.msg.mode.value = mode;
    req.pm.msg.mode.range = range;
    return ipq_netlink_sendto(h, (void *) &req, req.nlh.nlmsg_len);
}

/*
 * timeout is in microseconds (1 second is 1000000 (1 million) microseconds)
 *
 */
ssize_t
ipq_read(const struct ipq_handle *h,
	 unsigned char *buf, size_t len, int timeout)
{
    return ipq_netlink_recvfrom(h, buf, len, timeout);
}

int ipq_message_type(const unsigned char *buf)
{
    return ((struct nlmsghdr *) buf)->nlmsg_type;
}

int ipq_get_msgerr(const unsigned char *buf)
{
    struct nlmsghdr *h = (struct nlmsghdr *) buf;
    struct nlmsgerr *err = (struct nlmsgerr *) NLMSG_DATA(h);
    return -err->error;
}

ipq_packet_msg_t *ipq_get_packet(const unsigned char *buf)
{
    return NLMSG_DATA((struct nlmsghdr *) (buf));
}

int
ipq_set_verdict(const struct ipq_handle *h,
		ipq_id_t id,
		unsigned int verdict, size_t data_len, unsigned char *buf)
{
    unsigned char nvecs;
    size_t tlen;
    struct nlmsghdr nlh;
    ipq_peer_msg_t pm;
    struct iovec iov[3];
    struct msghdr msg;

    memset(&nlh, 0, sizeof(nlh));
    nlh.nlmsg_flags = NLM_F_REQUEST;
    nlh.nlmsg_type = IPQM_VERDICT;
    nlh.nlmsg_pid = h->local.nl_pid;
    memset(&pm, 0, sizeof(pm));
    pm.msg.verdict.value = verdict;
    pm.msg.verdict.id = id;
    pm.msg.verdict.data_len = data_len;
    iov[0].iov_base = &nlh;
    iov[0].iov_len = sizeof(nlh);
    iov[1].iov_base = &pm;
    iov[1].iov_len = sizeof(pm);
    tlen = sizeof(nlh) + sizeof(pm);
    nvecs = 2;
    if (data_len && buf) {
	iov[2].iov_base = buf;
	iov[2].iov_len = data_len;
	tlen += data_len;
	nvecs++;
    }
    msg.msg_name = (void *) &h->peer;
    msg.msg_namelen = sizeof(h->peer);
    msg.msg_iov = iov;
    msg.msg_iovlen = nvecs;
    msg.msg_control = NULL;
    msg.msg_controllen = 0;
    msg.msg_flags = 0;
    nlh.nlmsg_len = tlen;
    return ipq_netlink_sendmsg(h, &msg, 0);
}

/* Not implemented yet */
int ipq_ctl(const struct ipq_handle *h, int request, ...)
{
    return 1;
}

char *ipq_errstr(void)
{
    return ipq_strerror(ipq_errno);
}

void ipq_perror(const char *s)
{
    if (s)
	fputs(s, stderr);
    else
	fputs("ERROR", stderr);
    if (ipq_errno)
	fprintf(stderr, ": %s", ipq_errstr());
    if (errno)
	fprintf(stderr, ": %s", strerror(errno));
    fputc('\n', stderr);
}
